7-4 Cellular Transport

Chapter 7 Section 1 Passive Transport Cell Size Surface area-to-volume ratios affect a biological system’s ability to obtain necessary resources or eliminate wastes As cells increase in volume, the relative surface area decrease and demand for material resources increases More cellular structures are necessary to adequately exchange materials and energy with the environment

Chapter 7 Section 1 Passive Transport Cell Size

Chapter 7 Section 1 Passive Transport Cell Size The surface area of the plasma membrane must be large enough to adequately exchange materials In other words, smaller cells have a more favorable surface area-to-volume ratio for exchange of materials with the environment.

Chapter 7 Section 1 Passive Transport Cell Size Examples of how increasing surface area increases the function of the cell include Root hairs - increases water absorption in roots of plants Cells of the alveoli - increase gas exchange in the lungs Cells of the villi or microvilli - increases absorption of food in the intestinal lining

Root Hairs

Alveoli

Chapter 7 Diffusion Section 1 Passive Transport Recall that when organisms adjust internally to changing external conditions they are maintaining homeostasis One way cells maintain homeostasis is by controlling the movement of substances across their cell membrane. Cells must use energy to transport some substances across the cell membrane by active transport Other substances move across the cell membrane without any use of energy by the cell by passive transport.

Chapter 7 Diffusion, continued Random Motion and Concentration Section 1 Passive Transport Diffusion, continued Random Motion and Concentration Movement across the cell membrane that does not require energy from the cell is called passive transport. A difference in the concentration of a substance across a space is called a concentration gradient. Equilibrium is a condition in which the concentration of a substance is equal throughout a space.

Chapter 7 Section 1 Passive Transport Equilibrium

Chapter 7 Diffusion, continued Movement of Substances Section 1 Passive Transport Diffusion, continued Movement of Substances The movement of a substance from an area of high concentration to an area of lower concentration caused by the random motion of particles of the substance is called diffusion. Many substances, such as molecules and ions dissolved in the cytoplasm and in the fluid outside cells, enter or leave cells by diffusing across the cell membrane.

Chapter 7 Section 1 Passive Transport Diffusion

Chapter 7 Diffusion, continued Section 1 Passive Transport Because of diffusion, food coloring (blue) will gradually move through uncolored gelatin (yellow), as shown in the beakers below.

https://www. youtube. com/watch https://www.youtube.com/watch?v=VY0mZUDvbH4&index=3&list=PLqlJYrIFRy9W9Gh-PxERL7TYWgO3xYtSR

Chapter 7 Section 1 Passive Transport Osmosis The diffusion of water through a selectively permeable membrane is called osmosis. Like other forms of diffusion, osmosis involves the movement of a substance—water—down its concentration gradient. Osmosis is a type of passive transport.

Chapter 7 Section 1 Passive Transport Osmosis

Chapter 7 Section 1 Passive Transport Osmosis https://www.youtube.com/watch?v=La3mhoghCBQ&index=2&list=PLqlJYrIFRy9W9Gh-PxERL7TYWgO3xYtSR

Chapter 7 Osmosis, continued Section 1 Passive Transport There are three possibilities for the direction of water movement: Water moves out. When water diffuses out of the cell, the cell shrinks. A solution that causes a cell to shrink due to osmosis is a hypertonic solution. Water moves in. When water diffuses into the cell, the cell swells. This is a hypotonic solution. If too much water enters the cell it will rupture. No net water movement. A solution that produces no change in cell volume because of osmosis is called an isotonic solution.

Chapter 7 Osmosis, continued Section 1 Passive Transport In a hypertonic solution a plant cell will lose water, mainly from the central vacuole. The membrane shrinks away from the cell wall. This causes wilting. [plasmolysis] In a hypotonic solution the central vacuole fills with water, pushing the membrane against the cell wall. The cell becomes firmer because turgor pressure has increased.

Hypertonic, Hypotonic, and Isotonic Solutions Chapter 7 Section 1 Passive Transport Hypertonic, Hypotonic, and Isotonic Solutions

Crossing the Cell Membrane Chapter 7 Section 1 Passive Transport Crossing the Cell Membrane Diffusion Through Ion Channels An ion channel is a transport protein with a polar pore through which ions can pass. The pore of an ion channel spans the thickness of the cell membrane. An ion that enters the pore can cross the cell membrane without contacting the nonpolar interior of the lipid bilayer.

Chapter 7 Section 1 Passive Transport Ion Channels

Diffusion Through Ion Channels Chapter 7 Section 1 Passive Transport Diffusion Through Ion Channels

Crossing the Cell Membrane Chapter 7 Section 1 Passive Transport Crossing the Cell Membrane Facilitated Diffusion Most cells also have a different kind of transport protein, called carrier proteins, that can bind to a specific substance on one side of the cell membrane, carry the substance across the cell membrane, and release it on the other side. When carrier proteins are used to transport specific substances—such as amino acids and sugars—down their concentration gradient, that transport is called facilitated diffusion.

Facilitated Diffusion Chapter 7 Section 1 Passive Transport Facilitated Diffusion

https://www. youtube. com/watch https://www.youtube.com/watch?v=vKGN_Zhz8AY&index=4&list=PLqlJYrIFRy9W9Gh-PxERL7TYWgO3xYtSR

Passive Transport: Facilitated Diffusion Chapter 7 Section 1 Passive Transport Passive Transport: Facilitated Diffusion

Active vs. Passive Passive Transport = High Concentration  Low Concentration No energy expenditure from the cell. Active Transport = Low Concentration  high Concentration Energy need; ATP

Comparing Active and Passive Transport Chapter 7 Section 2 Active Transport Comparing Active and Passive Transport

Movement Against a Concentration Gradient Chapter 7 Section 2 Active Transport Movement Against a Concentration Gradient The transport of a substance across the cell membrane against its concentration gradient is called active transport. (Requires Energy) Most often, the energy needed for active transport is supplied directly or indirectly by ATP.

Chapter 7 Section 2 Active Transport Active Transport

Movement Against a Concentration Gradient, continued Chapter 4 Section 2 Active Transport Movement Against a Concentration Gradient, continued Sodium-Potassium Pump One of the most important membrane pumps in animal cells is a carrier protein called the sodium-potassium pump. In a complete cycle, the sodium-potassium pump transports three sodium ions, Na+, out of a cell and two potassium ions, K+, into the cell. Without the pump, the sodium ions in the cell would cause water to diffuse into the cell in turn causing it to burst.

Sodium-Potassium Pump Chapter 7 Section 2 Active Transport Sodium-Potassium Pump

Sodium-Potassium Pump Chapter 7 Section 2 Active Transport Sodium-Potassium Pump https://www.youtube.com/watch?v=P-imDC1txWw

https://www.youtube.com/watch?v=yz7EHJFDEJs

Chapter 7 Movement in Vesicles Section 2 Active Transport Movement in Vesicles Many substances, such as proteins and polysaccharides, are too large to be transported by carrier proteins. These substances are moved across the cell membrane by vesicles. The movement of a substance into a cell by a vesicle is called endocytosis. The movement of a substance by a vesicle to the outside of a cell is called exocytosis.

https://www. youtube. com/watch https://www.youtube.com/watch?v=qpw2p1x9Cic&list=PLqlJYrIFRy9W9Gh-PxERL7TYWgO3xYtSR&index=5

Endocytosis and Exocytosis Chapter 7 Section 2 Active Transport Endocytosis and Exocytosis

Endocytosis and Exocytosis Chapter 7 Section 2 Active Transport Endocytosis and Exocytosis

https://www.youtube.com/watch?v=prfMUwjobo8